OUR CHANGING GULF: THE ISLANDS
The islands of our much-loved Hauraki Gulf are showing some early signs of improvement. Thanks to the
efforts of committed councils, government departments and communities some of our islands and coastal
parks are being restored to their former glory. It is now possible to hear kiwi on Motuihe, bellbirds at
Tawharanui, saddlebacks on Rangitoto and Motutapu and even kokako on Hauturu / Little Barrier. The
dawn chorus is being restored to a growing number of islands and coastal sanctuaries and birds from these
sanctuaries are now spilling out into the surrounding countryside. Keeping these places pest-free requires
constant vigilance.
Just two life-times ago the skies around the Gulf darkened as millions of seabirds returned to their burrows at dusk and the
surrounding seas shimmered with vast schools of snapper, trevally and kingfish, followed by large numbers of gannets, dolphins and
whales. Today this richness is vastly reduced. The Hauraki Gulf Forum has a vision of more fish in the sea, more diversity, more kai
moana, and better recreational and economic opportunities. Three things need to change to ensure the Gulf continues to improve
and flourish: commercial and recreational fishers need to be able to exercise clear rights and responsibilities for an enhanced fishery,
regenerating marine areas are needed where life flourishes and rejuvenates our Gulf, and better rules are needed to limit pollutants
from intensive farming and urban development. We need to work together to protect and enhance the Hauraki Gulf Marine Park now.
Islands are true treasures of the Gulf. There are
estimated to be 425 islands in the Gulf, which range
in size from small reefs, stacks and sandbars to iconic
landforms covering thousands of hectares. These oases
of marine and terrestrial biodiversity are scattered
from the margins of the mainland to the edge of the
continental shelf. They influence currents, wind and
waves throughout the Gulf and provide precious habitat
for native plants and animals.
Feral Goat
Cook’s Petrel
The Cook’s petrel is one of 23 seabird species which
breed around the Hauraki Gulf (making it one of the
most diverse seabird populations in the world). The
black petrel, which only breeds on Great Barrier and
Little Barrier Islands, is threatened because of bycatch
in snapper and bluenose longline boats and trawlers, as
well as from land-based predators. The NZ storm petrel
was assumed extinct until rediscovered in the Gulf in
2003. Its breeding location is still unknown.
Rabbits
Island landforms, geology and ages vary widely around
the Gulf. Most of Waiheke and Kawau Islands were
created by very ancient deep-sea deposits that were
uplifted to form land. Great Barrier Island is mostly
covered by weathered volcanic rocks, which are 10-18
million years old. In contrast, Rangitoto is a “new” island
that emerged from the seafloor only 600 years ago.
Stoat
Hedgehog
Feral Cat
Bellbird
Mammals have been eradicated from 27 of the 62
islands that are larger than 10 ha. The eradication of
mammals has allowed many native species on those
islands to survive and flourish.
Forest recovery is being accelerated by replanting on
a number of inner Gulf islands. Much of this work is
being done by community groups, with the support of
DoC and councils. Care is taken to ensure that plants
are sourced locally and that a natural mix is grown.
On islands like Tiritiri Matangi, Motuora, Motutapu,
Motuihe, and Rotoroa native plants are now bursting
out of ground that was recently covered in pasture.
Hihi (female)
Hihi (male)
Kokako
Mature native forests originally covered the larger
islands in the Gulf, and still covers large parts of
Hauturu (Little Barrier Island). The composition of
Hauturu’s forest changes up its mountainous landscape
with broad-leafed forest on the coastal margin, northern
rata and tawa on the slopes, mixed kauri forest on the
ridges, towai and tawa further up and giving way to
quintinia, tawari and southern rata on the summit
ridge. This diverse forest is particularly important for
the survival of endangered native wildlife on the island.
Forest clearance has occurred on all of the large islands
in the Gulf. Forests were burned to clear land for
occupation, farming and cultivation, and trees were
logged for their timber.
Introduced mammals decimated native plants and
animals on islands by preying on vulnerable birds,
insects and reptiles, eating plants, and competing for
food and other resources. Luckily some of the worst
mammals never made it to all of the islands. Most
islands were kept free of possums. However, rats
became widespread, and species such as wallabies,
goats, pigs, rabbits and hedgehogs were introduced
to some islands. Cats were taken to islands as pets,
and some feral populations resulted. Cats are very
efficient predators of native birds, reptiles and large
invertebrates.
Many of our native species are still in serious trouble.
To restore the dawn chorus across the Gulf we need:
eradication programmes on islands where pests are
still present; prevention of reinvasion - through careful
checks by visitors for stowaway pests, and biosecurity
safeguards; habitat restoration and reintroduction of
species that have been lost. (See www.treasureislands.
co.nz for more info).
Endangered species are being moved (translocated)
to new islands to expand their populations and to
provide an insurance against single populations being
wiped out in catastrophic events. Where possible,
“translocations” include individuals from a variety of
sources so the genetic diversity of an island population
is maintained. Translocated species include endangered
birds such as kiwi, takahe, pateke (brown teal), North
Island weka, hihi, kokako and saddleback, reptiles such
as the tuatara and threatened geckos and skinks, and
insects such as the Mercury Island tusked weta and
giant weta or wetapunga.
Many species of native birds, reptiles and insects in
New Zealand have been decimated or lost as a result
of the effects of introduced mammals, habitat loss and
hunting. The islands of the Gulf are the final refuges
for some of our most vulnerable species. However, even
they cannot survive without careful management. For
instance, the last two kokako on Great Barrier Island
had to be moved to Hauturu (Little Barrier Island) in
1993 to ensure their survival.
Naturally regenerating forests are significant features on
many islands. These areas are recovering after the original
mature forests were burned or felled. Early-stage forests
are dominated by species like kanuka and manuka (i.e.
tea tree), which slowly give way to a succession of other,
larger canopy-forming species.
Many native species are flourishing in the absence
of mammalian predators. The effects of mammal
eradication have been remarkable, even on relatively
untouched islands such as Hauturu (Little Barrier
Island). The removal of cats and kiore (Pacific rats)
from Hauturu led to an explosion in the populations
of species such as Cook’s petrel, and allowed the
reintroduction of kokako and saddleback. The
pest eradication at Tawharanui has led to bellbirds
recolonising the park. They are now the most abundant
bush bird and sightings of bellbirds are occurring
increasingly beyond the park.
People now get to rub shoulders with rare native
species in open sanctuaries like Tiritiri Matangi and
Tawharanui, giving them a glimpse of our past. The
pest free sanctuary experience contrasts starkly with that
obtained from many now-silent mainland forests.
Saddleback
Green Gecko
A unique pohutukawa-rata forest is emerging from
the lava flows on Rangitoto Island. This is a particularly
harsh environment to grow in with little soil, blistering
temperatures, and virtually no fresh water.
Giant Weta
Kiore
Tuatara
PRODUCED BY
SPONSORED BY
ENVIRONMENTS OF THE HAURAKI GULF MARINE PARK
Project director: Tim Higham, Manager, Hauraki Gulf Forum | Text: Dr Shane Kelly | Art: Dave Gunson | Graphics: Kylie Hibbert, The New Zealand Herald | Thanks: Staff of Auckland Council and Department of Conservation | Source: State of our Gulf: Tikapa Moana - Hauraki Gulf State of the Environment Report 2011, available at www.haurakigulfforum.org.nz
IN ASSOCIATION WITH